Twenty people died when a boat on the Niger river broke up overnight near the central Malian city of Mopti, a rescue services official said Saturday, adding that another 23 people were missing. \"We don\'t know yet why the boat broke up,\" Commander Dramane Diallo told AFP, adding: \"Investigations are under way. The boat broke at the stern\" in a branch of the river near the village of Koubi, with 210 survivors.